No abstract

This research is aimed at predicting erosion and sedimentation in the Ghareh Aghach Basin in the central part of Iran using Erosion Potential Model (EPM) models incorporated into Geographic Information System (GIS) software. This basin has an area of about 8955 hectares. The region has a range of vegetation, geological, soil texture and land use types. The basin was subdivided into 5 sub-basins. Data required for this study were collected in part through published reports, whilst the remaining was derived by field surveys. Necessary maps in EPM models were prepared in Autocad-2006 medium and were transported to IILWIS, after some revision. After constructing topologies for all polygons, we entered weightings for all layers within the Arc-View software. Combinations of all layers were managed thereafter. Coefficient of each factor was determined, and erosion intensity coefficient (Z) was calculated. Four layers for EPM model were combined to develop the final layer of erosion and sedimentation. The results of the EPM model for homogenous and uniform sampling units showed that 0.19% (16.7 ha) of the total watershed area were classified as class I of erosion category with very low sedimentation and 15.1% (1352 ha) were classified as class II of erosion category with low sedimentation and 41.3% (3699 ha) were classified as class III of erosion category with medium sedimentation and 13.2% (1175 ha) were classified as class IV of erosion category with high sedimentation and finally 30.2% (2711 ha) were classified at class V of erosion category with very high sedimentation, respectively. The result of comparing erosion and sediment values using an EPM model with measured values showed that no significant difference was observed between the estimated and measured values (P , 0.05).

Studies of vegetation and soil dynamics on grazed and non-grazed rangelands are important prerequisites for improving range management. For this reason, the effects of excluding grazing animals for 26 years were studied on vegetation and soil dynamics at two rangeland condition sites (enclosure and exclosure) in Isfahan province, Iran. The vegetation cover and edaphic characteristics were studied simultaneously in both grazed and non-grazed range sites. In this study vegetation characteristics, as well as vegetation floristic, canopy cover, plant density, botanical composition, plant biodiversity and soil moisture infiltration were recorded during the grazing seasons of 2006 to 2007. Vegetation characteristics, in particular vegetation cover and plant density, differed significantly between the non-grazed (enclosed) and grazed sites and increased significantly in the non-grazed range site. The vegetation cover in the non-grazed site consisted mainly of class I and II plants while class III plants predominated in the grazed site. There was no significant difference in the botanical composition of the two areas. There was a significant increase in Gramineae in the enclosure site compared to the SWTOllllding grazed site, but there was a considerable decrease in forb species. We also observed a significant decrease in soil infiltration rates in the grazed range site compared to the enclosed range site. Litter content was higher inside and exposed bare soil greater outside the enclosure. Infiltration rates were higher in the enclosed area than in the grazed exclosure area throughout the grazing season. A comparison of vegetation and soil infiltration within the enclosure showed that vegetation condition and soil infiltration were good and that removal of grazing animals, as in the enclosure, causes an improvement in rangeland condition in this region.

In Malaysia, areas under oil palm plantations have increased dramatically since the early twentieth century and have resulted in multiple conversions of land change. This paper presents a spatial and temporal model for simulation of oil palm expansion in the Kuala Langat district, Malaysia. The model is an integration of cellular automata (CA), multicriteria evaluation (MCE), and Markov chain (MC) analysis while MCE provides transition rules of CA iterations and MC analysis assigns a transition probability to each single pixel at the time steps. Evaluation criteria consist of constraints and nine suitability factors indicating environmental and socioeconomic issues of oil palm development. In the first simulation, changes of six land-cover classes were projected to the year 2008 based on transitions between 1997 and 2002. Two measures of quantity disagreement and allocation disagreement were adopted to validate model outcome. The simulation of land-cover change of the year 2020 was done based on the transition observed between 1997 and 2002 regarding the satisfactory agreement of the projection and the reference data at the first simulation. The results, based on five landscape metrics, indicated continuous spatial patterns of oil palm plantations but more fragmented spatial patterns of other land classes by the year 2020.